The expression “biomass having a high solids fraction” is to be understood as meaning the opposite of liquid, pumpable biomass, such as is used in wet fermentation processes. “Biomass having a high solids fraction” should therefore be understood as non-pumpable biomass.
A biogas plant in accordance with the preamble of claim 1 is known from WO 2007/096392. This known biogas plant includes a plurality of digestion tanks which are adapted to be closed in a gas- and liquid-tight manner, each of which includes a percolate discharge conduit having a percolate pump and opening into a common percolate reservoir. Percolate may be conveyed back from the common percolate reservoir into the digestion tank via a percolate return line in which a percolate recirculation pump is provided and which branches toward the individual digestion tanks. The filling level or percolate level of the individual digestion tanks is detected by respective filling level sensors having the form of pressure sensors.
This known biogas plant has the drawback that the plurality of digestion tanks has to be considered as a homogeneous overall system, for each digestion tank receives the same percolate, with substantially identical conversion processes taking place in every digestion tank in this overall system. This known biogas plant is therefore homogeneous in terms of process technology and is cumulatively composed of a plurality of partial systems (the individual digestion tanks) as regards its capacity.